1. Field of the Invention
The present invention relates to a channel switching apparatus of a digital television and a method thereof, and in particular to a channel switching apparatus of a digital television and a method thereof which are capable of making identification of a channel easier by providing OSD information related to a channel to be switched to a user when the user switches the channel of the digital television up/down.
2. Description of the Prior Art
According to a start of a digital broadcasting, a plurality of forms of a reception apparatus for a digital television such as a direct view DTV receiving the digital broadcasting, a DTV set-top box etc. are developed, and are sold.
In general, in order to select a pertinent channel among a plurality of broadcast signals received to the digital television, PAT/PMT information or PSIP information is required, in order to display the select channel on a screen. The received digital broadcast signal is switched into a digital channel and is displayed on the screen. A good amount of time is required in order to display the digital broadcast signal on the screen.
An estimated required time for the display after the digital switching will now be described as below.
First, about 300–400 ms time is required for tuning and channel demodulation of a received digital broadcast signal.
In order to select a channel of the digital television, about 400–500 ms time for searching a PID (Packet ID) comprised in the digital broadcast signal with each mode is required.
There are two modes for the digital television. A PAT/PMT mode requires about 400 ms time in order to search the PID, and a PSIP mode requires about 500 ms time in order to search the PID.
For outputting the received digital broadcast signal as a perfect picture after transmitting it to a video decoder, maximum 728 ms are required because of 500 ms time for receiving an I picture and VBV delay.
After switching the digital broadcast signal into a digital channel, 100 ms of coding time is more required besides the maximum 728 ms for displaying a perfect picture.
In the PAT/PMT mode, the total required time for displaying a picture can be described as below Equation 1.
[Equation 1]400 ms+500 ms+500 ms+730 ms+100 ms=2230 ms
In the PSIP mode, the total required time for displaying a picture can be described as below Equation 2.
[Equation 2]400 ms+400 ms+500 ms+730 ms+100 ms=2130 msIn order to display the channel selected among the broadcast signals received by the digital television, about 2230 ms time is required in the PAT/PMT mode, and about 2130 ms time is required in the PSIP mode.
As described above, in the digital television, about 2 or 3 seconds are required in order to display the select channel on a screen. But this may cause unpleasantness and discomfort to a user by requiring some to select a request channel because each channel can display a received picture after displaying a black picture for 2 or 3 seconds. The above-mentioned problem is decreased according to the development of a hardware technology. However, instant channel switching is not improved, and accordingly it still causes discomfort to the user.
In addition, in order to select the pertinent channel among the digital broadcast signals in the digital television, the PAT information, PMT information and PSIP information are required.